Encoded sheet material

ABSTRACT

An encoded sheet material includes a sheet of material having a first surface, a second surface disposed opposite the first surface and an edge extending between the first surface and the second surface and peripherally about the sheet of material, the edge having indicia arranged thereon to form a code uniquely identifying the sheet of material. A system for managing an encoded sheet of material, includes a code reader operative in conjunction with the encoded sheet of material for reading the code, a sheet processing apparatus for reading information from and/or writing information to at least one of the first and second surfaces, and a processor in communication with the code reader device and the sheet processing apparatus for associating the information with the read code.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/643,628 filed Aug. 21, 2000 now U.S. Pat. No. 6,585,163, the contentsof which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to encoded sheet material, and moreparticularly to systems and methods for managing encoded sheet materialhaving information recorded thereon.

BACKGROUND OF THE INVENTION

Despite the publicity about the paperless office, paper remains animportant media in today's working environment. Many efforts have beenmade to integrate paper documents with computer-based informationsystems. These efforts generally involve two scenarios. The firstscenario involves scanning an existing physical document to create adigital copy, assigning a digital file name and then managing thedigital copy as any other digital file. The second scenario involvescreation of a physical document from an existing digital document orfile such as by printing. To aid in the integration process, a barcodeor a Dataglyph may be printed or otherwise attached to a physicaldocument. Dataglyphs are generally less visually disruptive thanbarcodes. Both barcodes and Dataglyphs provide a means for the computerto grasp intentionally printed information on the paper document. Sinceboth are generally applied at the time the information is recorded onthe sheet of paper (but may be applied later through the use of anadhesive label), both generally appear on the same face of the sheet ofpaper as the recorded information.

At the organization level, many documents, such as contracts, reports,files, technical documentation, etc., have to be physically stored forlegal, administrative or operational reasons. Attention must be paid totheir indexing and classification in order to keep document retrievalcost at an acceptable level. One solution is to physically attach abarcode or Dataglyph to an existing paper document and scan the documentinto the computer-based information system.

Having a record of a paper document in a computer-based informationsystem does not solve the problem of knowing where the actual paperdocument is located. Even if location information is stored at the timethe paper document is input into the system (such as when the barcode orDataglyph is read by the computer-based information system), the paperdocument may have been moved when a user retrieved it and later replacedit.

Most paper documents in offices do not contain barcodes or Dataglyphsand are not part of a computer-based information system. Most officeshave piles of document on shelves, desks and the like that areclassified in an ad-hoc and personal manner. Finding a document in oneof these ad hoc filing systems often means browsing through severalpiles to find a particular document.

The verification that a paper or hard copy version of a document is anoriginal, as opposed to a copy or imitation, is important in manybusinesses and legal transactions. Examples include contracts, stockcertificates, bank notes, premium bonds, etc. Verification ofauthenticity of an original document has become harder to perform sincemodern techniques enable the production of high quality copies which arefrequently difficult to detect from the original. Even if an originalpaper document included a barcode or Dataglyph on the face of thedocument, any copy of the paper document will also include the samebarcode or Dataglyph.

Much work has been done in order to verify the integrity of the contentof a hardcopy document as well as its origin (this is referred to asauthenticating a document). Verifying the content and origin(authenticating) of a hard-copy document consists of making sure thatits content was not tampered with, and that it really originates fromthe supposed source. This prevents manipulation of the content of adocument, while true (i.e. not manipulated) copies remain possible.Originality check is concerned with discriminating copies from theoriginal hardcopy document. The problem of originality is closelyrelated to the problem of authentication because in most cases whereoriginality is important, the content is also important. However, insome cases the originality of a sheet of paper itself is important,independently of its content. Consider for instance the case of a sheetof paper being circulated to collect signatures for a petition. When itcomes back, the originator expects to have the original sheet (and not apossibly manipulated copy).

The use of edge marking of sheet materials has been proposed for variousapplications. U.S. Pat. No. 5,085,417 to Copham, Method of EncodingStacks of Printed Materials, describes a process for using edge markingsto identify one customer's order for form checks from anothercustomer's. During manufacture of a sheet of checks, a coded image isprovided at the cutting boundaries of the stock sheets, so that when thechecks are cut from the stock, an identification code appears on thechecks when viewed from the edge. The edge-visible code is obtained bycutting the paper precisely where marks are located. A different code isprovided for each customer to enable workers to look at the stackedcheck books at the edge to determine if another customer's checks wereerroneously placed.

U.S. Pat. No. 6,335,084, “Encoded Sheet Material and Sheet ProcessingApparatus Using Encoded Sheet Material”, which is assigned to the sameassignee as this application, describes pre-marking of edges of paperreams/stacks (during manufacture) with information related to thepaper's physical properties (e.g., its weight, color). This encodedinformation is read and used by printers (and other recording deviceswhich record information on the faces of the sheet material) whenselecting paper from paper trays.

SUMMARY OF THE INVENTION

An encoded sheet material, according to the invention, includes a sheetof material having a first surface, a second surface disposed oppositethe first surface and an edge extending between the first surface andthe second surface and peripherally about the sheet of material, theedge having indicia arranged thereon to form a code uniquely identifyingthe sheet of material. A system for managing an encoded sheet ofmaterial includes a code reader operative in conjunction with an encodedsheet of material for reading an edge code; wherein the encoded sheet ofmaterial has a first surface, a second surface disposed opposite thefirst surface and an edge extending between the first surface and thesecond surface and peripherally about the sheet of material, the edgehaving indicia arranged thereon to form a code uniquely identifying thesheet of material; a sheet processing apparatus for reading informationfrom and/or writing information to at least one of the first and secondsurfaces of the encoded sheet material; and a processor in communicationwith the code reader and the sheet processing apparatus for associatingthe information with the edge code.

By providing each sheet of material with a unique edge identifier, anyinformation that may be recorded on the sheet of material may beassociated with that sheet of material. By placing the unique identifieron the edge, both surfaces are available for recording information. Theedge marking can be made with a visible or an invisible ink. If therecording device includes an edge reader coupled to a processor with amemory, whenever a user makes a copy of an electronic file, therecording device reads the edge marking on each sheet of material used,and the processor associates that sheet of material with the electronicfile. This association can be stored in memory. This feature is usefulfor tracking or monitoring physical copies of an electronic file.Additional information or meta data may also be associated with theelectronic file.

The association information may be stored and used for other purposes,such as monitoring the number of copies made of a particular file, formonitoring the location of the copies and for monitoring the number ofsheets of material used. The association information can be made orupdated at any time. For example, if an electronic file is printed on asheet of material with a unique edge marking, that association may bemade and stored in a memory at the time of printing or later. If thatrecorded sheet of material is used to make a photocopy, an edge readerin the copier can make an association of the read edge marking of the“original hard copy” with the edge marking of the sheet of material usedto make the photocopy. This information may be stored in memory and canbe used to update the association information with the originalelectronic file and create a new association for the “original hardcopy.”

Retrieving information associated with a sheet is accomplished byreading its edge identifier and querying the infrastructure to retrievethis information, given the identifier. Preferably, sheets of materialare pre-marked at production time. If pre-marked at production time,each sheet can be given a code identifying the ream to which it belongsas well as uniquely identifying that sheet. The code can include aportion identifying the ream, manufacturer, and other information that auser might require. Some reams of sheet material may be specially codedwith special visible and/or invisible inks and used as special bondpaper for financial instruments, for example. Indeed, some organizationsmay wish to reserve special reams of material.

Edge-readers can either be embedded in the recording devices (such asprinters, facsimile machines, photocopiers, shredders, etc.) or affixedin work places (e.g. desktops). The edge readers are coupled to acomputer or network where the read association information may be readand/or written. The edge readers enable the automatic association ofprinted-sheet <-> document. Users may also use any sheet of a documenteither to obtain related service by passing the sheet through anedge-reader, or to establish an association in a similar way.

Documents in paper form are largely used in almost all businesses.Documents are frequently stored in an ad-hoc manner (e.g., on personalshelves in an office) or formally (e.g., legal or contractual documentsare stored in filing cabinets, etc. in banks, administration offices,etc.). Document classification and retrieval is often problematic andcostly. The method of the invention provides computer support to thesetwo tasks, without disrupting the user's normal work practice, andrequires less effort. The invention enables documents to beautomatically indexed in place (i.e., in their normal storage area) andretrieved by obtaining storage information from a computer-based system.

The encoded sheet material of the invention may be used to index andmanage physical documents. Indexing and managing physical documentsgenerally involves four steps. First, the physical documents must beindexed, which often includes generating some form of unique identifier.Then the physical documents must be inserted in the storage area, i.e.,in accordance with some classification scheme. Retrieving the storedphysical document involves searching through the storage area using theclassification scheme. Finally, after use, the document must bere-inserted into the storage area, which location may be different fromthe original location.

Physical documents may be edge marked and the edge markings used toindex and retrieve them from their storage locations. A method ofmanaging a physical document, wherein the physical document includes atleast one sheet of material, includes marking an edge of the at leastone sheet of material with indicia arranged to form a code identifyingthe sheet of material, storing the physical document in a storagelocation, indexing the physical document by associating the code withthe storage location, and storing the indexing information in acomputer-based information retrieval system. A method of retrieving aphysical document stored in a storage location, includes obtaining acode associated with the physical document, wherein the physicaldocument includes at least one sheet of material having a first surface,a second surface disposed opposite the first surface and an edgeextending between the first surface and the second surface andperipherally about the sheet of material, the edge having indiciaarranged thereon to form the code identifying the sheet of material, andinformation recorded on at least one of the first and second surfaces ofat least one of the sheets of material, using a scanning device to scanthe storage location for the code, and when the output of the scanningdevice indicates the location of the sheet of material having code,retrieving the physical document.

The invention provides a computer-implemented system for the indexing,storage and retrieval of paper document from piles, filing cabinet,shelves and more generally from document storage areas where documentedges are visible. By using a robust code, such as a large barcode onthe edge of the documents, which is visible (to the particular scanningdevice) on the edge of the documents, physical documents may be inputinto a computer-based system and located for retrieval. In addition tostoring the edge codes and location information, images of the storagearea (shelves, piles, etc.) may also be stored in the computer-basedsystem. Documents can be located by scanning the storage location forthe document's edge code or by accessing the computer-based system andretrieving the storage location.

Since each sheet of paper holds a unique identifier (preferably)pre-marked on its edge at production time, indexing is automatic; thepre-marked edge codes constitute the minimal required index. However,this does not preclude the use of other forms of indexing, in addition.Since the physical documents can be easily retrieved (by scanning stacksof files for their edge codes), storage of physical documents becomes assimple as stacking documents as they arrive. However, any otherclassification scheme can also be used. Documents must be stacked sothat the edge codes can be read. Physical document retrieval is computeror network supported; the computer or network indicates via an outputdevice where the document is located. For example, the computer maydisplay an image of the storage area where the document is located.Re-insertion of a physical document is equally simple.

An original document is one from which a copy, reproduction ortranslation is made. In the case of a contract, the original contract isthe one (or ones in the case of duplicate originals) with the originalsignatures affixed to it. Originality goes to a document's content aswell as physical integrity (i.e., the particular sheets of paper used).Authenticity of a document goes to the integrity of the information,i.e., whether the information conforms to the information in theoriginal. An authorized copy of an original document, is authentic if itconforms to the original so as to reproduce essential features. Theinvention enables the authentication of originals as well as copies. Theinvention provides a method of authenticating the sheets of paper(material) on which documents are recorded as well as authenticating theinformation on the sheets of material.

A method of creating an authenticatable sheet of material, according tothe invention, includes measuring at least one physical property of thesheet of material; marking an edge of the sheet of material with indiciaarranged to form a unique code identifying the sheet of material,wherein the sheet of material includes a first surface, a second surfacedisposed opposite the first surface and an edge extending between thefirst surface and the second surface and peripherally about the sheet ofmaterial; and recording the measured physical property in a measuredatabase indexed by the edge code. To verify the validity orauthenticity of a sheet of material, the edge code is read, the samephysical property is measured and the measured value is compared withthe previously stored value extracted from the measure database. If thetwo are substantially equal, the sheet of material is authentic.

The use of edge codes and physical property measures can be used toauthenticate a document, i.e., a sheet of material on which informationhas been recorded, and verify its originality. A method of creating anauthenticatable physical document which includes information recorded ona surface of the sheet of paper includes using the edge code with theinformation to generate an encryption hash, digitally signing theencryption hash and recording the digitally signed encryption hash on asurface of the sheet of material. If a physical property has beenmeasured and indexed in a measure database, the originality of the sheetof material can be verified as well. A digital signature does not hidethe content of the information, but is used primarily to guarantee theidentification of the sender of the information and its integrity. Foradded security, the encryption hash may be encrypted rather than justdigitally signed.

Verifying the authenticity of a sheet of material involves reading thedigitally signed hash on the document, decrypting it, generating a newhash from the edge code and a portion of the information. The twoencryption hashes are then compared. If they are equal, the document isauthentic. Additionally, the edge code can be used to determine if thesheet of material is original, by measuring the physical property andcomparing its value to the value stored in the measure database.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an example edge marking according to theinvention;

FIG. 2 is a diagram of a scheme for an edge marking including a reammarking and individual sheet marking;

FIG. 3 is a perspective diagram of an edge reader reading an edge-markedsheet of material;

FIG. 4 is a schematic of an apparatus for managing a sheet of materialaccording to the invention;

FIG. 5 is a flow chart of a method of indexing and retrieving physicaldocuments according to the invention;

FIG. 6 is an example of 12 characters in Code 39 barcode;

FIG. 7 is an example of the code “E-PLACARD” in Code 39 barcode;

FIG. 8 is a photograph of a 30-page document with the code of FIG. 7;

FIG. 9 is a photograph of the barcode extracted from FIG. 8 and enlargedvertically;

FIG. 10 is a photograph of a screen showing the results of a standardbarcode reader reading the barcode in FIG. 8;

FIG. 11 is a photograph of an image of the location of the E-PLACARDdocument;

FIG. 12 is a schematic of a method of creating an authentic physicaldocument;

FIG. 13 is a schematic of a method of authenticating a physicaldocument; and

FIG. 14 is a schematic of a method of authenticating a sheet ofmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Most sheets of material, such as paper sheets have six faces, two ofthem being commonly used: the so-called recto (first surface) and verso(second surface). The four other faces, the edges, may be used touniquely identify each sheet and, optionally, the ream it comes,manufacturer and so on. If a ream identifier is used as part of theunique sheet code, each sheet in the ream will receive the same uniqueream identifier, in addition to a unique sheet identifier. Theseidentifiers can be marked with visible or invisible ink.

Typical A4 paper sold today presents on the long and short edges acombined edge surface of 297×0.1 mm² and 210×0.1 mm², respectively. Arobust code can be easily devised to fit within this size constraint. (Arobust code is one which can be easily read on the edge of a singlesheet of material and also affords a sufficiently large number of codesfor the anticipated amount of sheets of material to be used.) Forexample, a 64 bit long code made of 1 mm wide bars on a 2 mm grid wouldrequire 128 mm, which leaves enough room (say 64 mm for 32 bits of errorcode) for error correction code. In total this code (with errorcorrection) would require 192 mm, and would also fit on letter sizesheets (8½ inches by 11 inches). A typical edge thickness of 0.1 mm issufficient height to write the bar constituting the code. For instance,to give an order of magnitude, the dots of a 600 dpi printer are 0.04 mmhigh. Two of these dots fit on the edge height of 0.1 mm. Thus the edgesurface of typical paper sheets is thick and long enough to hold theexample robust codes. A 64 bit long code provides enough unique codes toenable each inhabitant of the earth to consume 80,000 sheets of paper(material) per day for over 100 years.

There are many schemes which may be used to create a unique code to markthe edges of sheets of material. In addition to a unique sheetidentifier, the edge code may also include information identifying themanufacturer, date of manufacture, a ream identifier, etc. Two specificexamples will be described herein, however, the invention is not limitedto only these two. The exemplary coding schemes described below includea unique sheet identifier and a ream identifier.

The first scheme uses the long edge for the sheet identifier and theshort edge for the ream identifier. Referring to FIG. 1, a sheet ofmaterial, such as paper, 10 includes long edge 13 and short edge 11.Long edge 13 includes ream identifier 14; short edge 11 includes uniquesheet identifier 12. While both identifiers are shown in FIG. 1 as bars,other forms of markings may be used, such as diagonal lines, dots andthe like. These marks may be visible or invisible. Optional recordedinformation 16 may be recorded on surface 15 of sheet 10.

The second exemplary coding scheme codes the ream and sheet identifierson the same edge, thus allowing pre-marking of the two identifiers onall four edges, which may be advantageous for some applications.Referring to FIG. 2, ream 20 includes a plurality of individual sheetsof material 10 (typically there are 500 sheets in a ream). In thiscoding scheme, the ream identifier and sheet identifier are on one edge.A ream identifier 22 is pre-marked at one section of the combined edges.In this embodiment, the ream identifier consists of bars. The sheetidentifier is created by offset line 24, drawn across the entire ream.This marking scheme enables pre-marking of the entire ream at the sametime. The offset 25 between the offset indicator mark 27 and the end ofthe paper edge 29 is sufficient to discriminate each sheet of a ream.

In this example, the value of unique identifier for sheet M of a ream ofN sheets of material may be computed as the distance 23 or as the ratioof the distance 23 over the entire distance 23+25. This value inconjunction with the ream portion 22 provides a unique identifier forsheet M. Ream identifier 22 may also include manufacturer name, date ofmanufacture, type of sheet material, etc.

For a typical 20 pound ream of photocopy paper (height of 5 cm, sheetthickness of 0.1 mm, and 20 cm of the ream edge dedicated to the offsetline), the offset of two consecutive sheets is 0.4 mm. In addition,drawing thicker lines parallel to the offset indicator line 24 willassist the edge reader device evaluate each sheet offset (because of theregularly distributed small plots on the edge of each sheet). Otheralternatives exist, such as any asymmetric curvilinear function drawn inplace of straight line 24 (provided the curve provides a unique code foreach sheet).

By marking sheets of material at production time with industrial means,invisible inks, fluorescent dyes or other technical inks may be used (inaddition to standard visible inks or a combination of visible andinvisible inks). While it is anticipated that most sheets of materialwill be pre-marked, i.e., during manufacture and before an informationis recorded on the surface, pre-marking is not required. Edges may bemarked with a code after a sheet of material has been printed orrecorded with information. Edge marking after information is recorded isuseful for existing physical documents, such as reports, articles,magazines, books, etc.

An edge reader is used to read the edge code on a sheet of material orphysical document. Edge readers may be employed on desktops asindividual units or embedded in devices such as facsimile machines,printers, copiers, shredders, etc. An example of an edge reader is shownin FIG. 3. Other edge readers may be used, such as a video camera orlight pen. Referring to FIG. 3, a sheet of material 10 with a markededge 12 passes through edge reader 30. The edge reader 30 reads the edgecode, generates an edge code read signal and sends it to computer 110 ornetwork 100. Computer 110 or network 100 associates the edge code isassociated with other information about the physical document 10, suchas whatever information is recorded on a surface of sheet 10. Asdescribed below, the edge code can also be associated with storagelocation information of the physical document.

Manual readers may be installed in any place where they allow users toconveniently read the edge identifier of a sheet of material. Typically,such a reader is affixed on the user's desk and connected to a desktopcomputer. An edge reader may include digital circuitry coupled with abar sensor in front of which the sheets are translated (either manuallyby the user, or automatically when embedded in another device). The barsensor may be an LED and sensor couple, without any mechanical parts.The digital circuitry decodes the edge-printed identifier, possibly inreverse direction because of possible rotations of the sheet of paper.

Referring to FIG. 4, a system for managing a sheet of material is shown.Sheet of material 10 is pre-marked during manufacture with a unique codeon an edge. Sheet 10 is provided to edge reader 30 which reads its codeand provides it to processor 50. Sheet 10 may also be provided to sheetprocessing apparatus 40 which may be a printer, which will printinformation from a digital file onto a surface of sheet 10 or a scanningdevice which will read recorded information from a surface of sheet 10and create a digital file from it. Edge reader 30 and recording device40 may be separate devices or edge reader may be embedded in recordingdevice 42. Recording device 40 reads or writes recorded information toprocessor 50. Processor 50 associates the read edge code with therecorded information and stores the association in memory 52.Alternatively, processor 50 may store the association information on anetwork 60. Each time the sheet 10 is processed by edge reader 30 and/orrecording device 40, the association information may be updated.

In addition to creating associations between sheets of material anddigital files, associations may be retrieved using the method and systemof the invention. If a physical document includes at least one sheet ofmaterial with an edge code (and presumably recorded information on atleast one of the sheets), the sheet of material may be read by an edgereader coupled to an information retrieval system. If the read edge codehas been previously associated with some information, that informationwill be retrieved by sending the sheet of paper through an edge readerand searching for any stored associations with that edge identifier.

Various infrastructures may be used to associate a sheet of materialwith an edge code identifier with some information, and to retrieve thelatter given an identifier. In particular the infrastructure disclosedin co-pending, co-assigned U.S. Pat. No. 6,330,976, “Marking Medium Areawith Encoded Identifier for Producing Action through Network” and U.S.application Ser. No. 09/276,532 filed Mar. 25, 1999, “Obtaining NetworkAddresses from Identifiers” may be used. These applications describe howa coded number is resolved to the Internet address of a document (oraction) through indirection via a centralized router and devisesefficient routing schemes (which allow codes of the order of 64 bits).Because of the indirection level provided by the router, paper can besold with the code pre-marked on their edges; association with anexisting reference may be done a posteriori through a software processof linking the code to the document address in the routing tables.

Because of the important role of paper in workplaces, the ability toeasily associate any piece of paper with electronic information is anessential feature for creating and developing knowledge sharingsolutions. For example pre-marking of unique identifiers on paper sheetsmakes it possible to turn any page of a user's documents into a documenttoken. There is no need to print additional machine-readable code, sincethe sheets are pre-marked, but only to associate the pre-markedidentifiers with the electronic document, or with whatever is needed forfurther usage as document token.

For example, if sheet processing devices which output printed paper(printer, fax, copier) are equipped with an edge reader and connected tothe infrastructure of the above described co-assigned applications, itis possible to associate every printed sheet with application-relevantinformation. For example, a printer associates the produced documentwith some electronic information, by associating (the range of) theidentifiers of the constituting sheets with it. Optionally, only thefirst and last sheets are pre-marked sheets in order to reduce thevisual “gray” effect on the edge of printed document (two differentpaper stacks may be used, one with pre-marked paper and the other withnormal paper). The copier associates the identifier of the originalpaper to its copy's identifier, or possibly resolves the former beforeestablishing the association. A facsimile machine works similar to theprinter. In turn, the printed document is known to the system and any ofits sheets can act as a document token once passed in an edge reader.

Thus a reprint may be obtained by reading the edge of a document sheetat a “reprint” edge reader affixed close to a printer or copier. Theelectronic version of a document may be opened on a computer by passingthe printed version in the desktop edge reader.

Uniquely identified sheets may be used in conjunction with the systemdescribed in U.S. Pat. No. 6,330,976 dealing with the recognition of thedocument the person is using. By combining the two, “Intelligent Papers”may be easily produced. Either the publisher prints the document on anedge-reader-equipped printer to establish the association between thepaper document and its electronic counterpart, or it associates thedocument with the pre-printed ream identifier(s). The latter appliesparticularly well for large volume as it avoids reading each sheetidentifier when printing and as it reduces the infrastructure load forassociation and resolution. The device used by the user must be equippedwith an edge reader in order to identify the electronic counterpart ofthe document (by querying the normal Intelligent Paper infrastructure).

Visible edge codes can be used to index, store and retrieve physicaldocuments. A visible code may be one that is visible to the eye, and itmay also be one that is invisible to the eye and visible to a detector,such as an infrared detector. A flow chart of the various steps in themethod is shown in FIG. 5. The first step is to mark the edge of atleast one sheet of a physical document (step 70). Preferably this isaccomplished during manufacture of the sheet of material (such aspaper), but it may also occur after manufacture. For multi-pagedocuments, one or some or all of the individual sheets may be edgemarked with an identifying code. The code is associated with thephysical document, such as by document meta data (e.g., URL, title,author, type, topic, date, file name, or some other convenient referencethat may be user selected). Associating the code with the physicaldocument ties the content of the document to the sheets of material.

In step 72 the physical document is stored in the desired physicalstorage location (e.g., pile of documents on a desk, file drawer, room,etc.). In step 74 the code is associated with the actual location instorage of the physical document. In step 76, the location associationinformation is stored in a memory. The association information includesdocument code and location information. It may also include the metadata previously associated with the code. An image of the storagelocation where the physical document is located may also be associatedwith the code.

If a document is already in a storage location and it has an edge code,but it has not been indexed into the system, it can be indexed byscanning the storage location for the document's code (step 78). Whenthe code is located (step 80), the storage location is associated withthe code (step 74) and that information is stored in memory (step 76).

Retrieving a document indexed in the system is accomplished by searchingthe system's memory for the document's code (step 82), reading thelocation information associated with the code (step 84) and thenretrieving the document from the storage location (step 86).

There are several ways to make visible a code on the document edge andto establish the association between the edge-visible code and adocument. Preferably, the edge of paper sheets is pre-marked atproduction time with a code uniquely identifying each sheet and eachream of paper; a software infrastructure that permits associating theedge code with some data relevant to the document (usually theidentity—such as the URL of the document—but possibly also with metadata) is provided and edge-reader are provided both embedded in deviceslike printers and copiers and provided to users as a desktop tool.

The edge marking scheme shown in FIG. 2 may be used. Since mostdocuments will contain several pages, we are interested in the visualeffect of stacking the sheets of a document, where the ream identifiersand offset indicators become aggregated. It is reasonable to assume thatin most cases, most of the sheets of a document come from the same ream.Because several sheets of the printed document have the same reamidentifier, this identifier will become clearly visible on the documentedge. In a similar manner, the document edge will exhibit a portion ofthe offset indicator line, as shown in FIG. 2.

The combination of the aggregated ream identifier and offset lineportion uniquely identify the document. Note that these marks may beinvisible to the human eye because they are marked with invisible ink,or semi-visible. In some situations it may not be necessary to read theentire code on each sheet of paper. A simplification of the method maybe made by using only the ream identifier. The retrieval service may beslightly degraded; the computer system may indicate several locationsfor the requested document, corresponding to the several documentsprinted from the same ream. An advantage of this simplified versionresides in easier image processing, in particular if only the reamidentifier is written on the short edge of sheet and is therefore verylarge. This simplified version may fit well in office settings, whereseveral users share a printer and there is little chance the same userwill obtain several documents from the same ream.

In addition to the edge marking described above, other methods ofmarking edges of sheets of paper may also be used in the indexing,storage and retrieval method.

Once a code is provided on the edge of at least one sheet of thedocument, the code may be associated with the document or the documentmeta data in one of several ways. Preferably, the association isestablished at print time in an automatic manner as described above. Theprinter is equipped with an edge reader, which decodes the unique sheetidentifier, and establishes the association between the document and thesheet identifier. For the association, the infrastructure described inco-assigned U.S. Pat. No. 6,330,976 and patent application Ser. No.09/276,532 may be used. Very little modification is required toimplement this system; the printer must have an edge reader embedded orcoupled to it. Paper surfaces are free from any mark and can beimprinted with any content. Alternatively, the user may explicitlyestablish the association once the document is printed, by presenting itto a sensor (edge reader, camera, scanner).

Location information can be stored as an image with the documentassociation information. A camera can be used to obtain an image of thedocument in the storage area. The image can be grabbed either on demand(when a search occurs) or periodically to maintain an up-to-date indexof location of documents. The latter also permits reporting on documentavailability and in some way tracking document usage. An inventory ofstored documents is also available to the user.

Because of resolution issues, one image may not be adequate to identifyand read edge codes. Obtaining a higher-resolution image of the storagearea, in particular for large areas, is possible, for example, byoverlapping snapshots. If overlapping snapshots is insufficient tolocate a document, image mosaicking may be used, but is computationallymore costly (in order to stitch together slightly high-resolutionoverlapping snapshots). Once the computer has determined the location ofa searched document, the location may be communicated to the user bydisplaying n image of the storage area, for instance, with the exactlocation of the document highlighted in the image. This provides anatural and intuitive way of communicating location to users.

In addition to cameras, a laser detector coupled with a laser beam maybe used to point out the document to the user. A more futuristicapproach would be for the user to wear a computer equipped with acamera, and to have a glass-mounted screen. Augmented reality techniqueswould then allow the user to directly see where the document is withinthe storage area.

The identification of regions holding a code and its decoding requiresimage-processing techniques. In order for these techniques to work, thecode must have sufficient resolution. While many different codes may beused and have the required resolution depending on the image processingequipment used, we have demonstrated the feasibility of a widely usedbarcode named Code 39. Encoding codes of the order of 2⁶⁴ bits requires12 characters, given the alphabet of 42 symbols of the Code 39. Eachcharacter encoded in a Code 39 symbol is made up of 5 bars and 4 spacesfor a total of 9 elements. Each bar or space is either “wide” or“narrow” and 3 out of the 9 elements in any given character are wide,giving the code its other name—Code 3 of 9. Consider narrow bars of 1.25mm and wide bars of 2.5 mm. The 12-character code has a total length of196 mm, and fits on the short edge of a sheet (see FIG. 6). For the longedge, much thinner bars can be used to preserve room for the offsetindicator line. For example, using more classical 0.25 mm width barsmakes the code length back to 4 cm.

Consider now that a camera with a 1600×1200 pixels resolution grabs onepicture of an area of 1 meter×0.75 meters]. Each pixel represents 0.625millimeters×0.62 millimeters. Two pixels cover the width of one narrowbar. Four pixels cover the width of a wide bar. This fits our needs,while not taking into account higher resolution obtained via imagemosaicking. There may be a problem for documents that do not exhibit aclear image on their edge, e.g. there is no block of contiguous pagescoming from a single ream that is large enough to form an image. Thiscan happen for a very small document, or for a document spanning overseveral reams. The case of paper jam may also slightly trouble the imageof the offset line, although probably not seriously. All of theseproblems can be handled in two complementary ways. First, the printercan detect these problems when they occur, because it reads the edgeidentifier of each sheet. Once a serious problem is detected, it cannotify the user and print the document again if the problem wastransient (paper jam, several reams). Small documents may possibly notwork at all, unless additional blank pages (or some special separators)are added to them. Second, the user can detect these problems simply bylooking at the edge of the document (if ink is visible or semi-visible).

To demonstrate the method of the invention, a 30-page document edgemarked on the bottom (short edge) of each page the barcode shown in FIG.7. The barcode was printed at the bottom of each page using MicrosoftWord with a zero width margin on a Xerox DocuPrint 4517. The barcode isactually at the bottom of the page, bleeding over onto the edge. Whenthe 30-page document is stacked in with a group of unmarked documents,the stacked, the document edge appears as shown in FIG. 8. FIG. 8 is aphotograph of the document taken with a Kodak digital camera DC50 at aresolution of 756×504 pixels. The picture covers approximately 30 cm×20cm. FIG. 9 is a photograph of the barcode extracted from FIG. 8 andenlarged vertically. A standard barcode reader was able to read theencoded value: E-PLACARD (see FIG. 10). When queried for the location ofthe document encoded E-PLACARD, the system returns the image shown inFIG. 11 with stored association information.

A method of creating an authenticatable sheet of material includes usingthe sheets of material with unique edge codes described above. For eachuniquely identified sheet of material, such as paper, the measure ofsome physical property is taken, preferably at production time (themeasure could be taken any time before the sheet of material is to berecorded with information). The measure is recorded in a measuredatabase indexed by the edge code (sheet identifier) of the sheet ofmaterial. The proof of originality of an individual sheet of paper isestablished by measuring again the same physical property and bycomparing the measure to the original one obtained from the measuredatabase. The unique identifier (edge code) of each sheet of materialpermits retrieval of the original measure (taken at production time orsome previous time) from the database).

One or more physical properties may be measured and the measured valuestored in the measure database. For paper materials, paper fiberarrangement or ink penetration may be measured. The infrastructure forassociating information with a sheet of material described above may beused to associate the measured physical properties with the sheet ofmaterial's edge code. The physical property information may also beassociated with any physical document (in which information such asarticle title, file name, URL, etc. is also stored). For securityreasons, the physical property information may be password protected orotherwise securely protected.

Having a measure database for storage of measured physical property maybe preferred by some users. Others may wish to store the measuredphysical property values locally in their own database where otherassociation information is stored with the edge code. Still other usersmay wish to have the measured physical property information encryptedand recorded or marked on the edge. An edge reader when reading theencrypted edge code would have to send the read encrypted portion to adecryption device or ignore it if physical property data is not needed.

In a typical hard copy authentication process, a hash-value is createdon the basis of the document content, for example, by scanning it,extracting text and picture characteristics and compressing thisinformation (with loss) into a hash-value. The hash-value is digitallysigned (it may also be encrypted if the content is to be hidden) andprinted on the document itself, for example, using a privatecryptographic key to sign the hash-value and printing it as a Dataglyphor barcode on the bottom of the document. Authentication consists oftaking the Dataglyph marked document, computing the hash-value given thetext of the document, reading the signed hash-value printed on thedocument, and validating it against the computed one using the publiccryptographic key.

The invention can also be used to extend existing hardcopy documentauthentication methods by inserting the unique edge code of theparticular sheet of material in the document's authentication stamp.Referring to FIG. 12, document 200 includes document text 204 which isprinted on the surface of a sheet of paper which has been edged markedwith edge code 202. An encryption hash 206 is created using both edgecode 202 and a portion of text 204. The hash 206 is then digitallysigned (or optionally encrypted) 210 using private key 208. Thedigitally signed (or encrypted) hash is then printed as a Dataglyph 212on document 200. Preferably the digitally signed (or encrypted) hash isprinted as a Dataglyph, but any other recording method or format, suchas a barcode, may be used. The Dataglyph may be recorded on any portionof the sheet of material: first or second surface or on an unusedportion of the edge.

By using edge coded sheets of material that have been additionallypre-notarized, i.e., the validity of the identifier of an individualsheet can be verified by reference to a measure database, retrieving thepre-measured physical property and comparing it to the measured value,pre-notarized paper prevents a forger from producing a sheet of paperwith a duplicate edge code. A forger may still damage the edge code,rendering authenticity and originality in question. Pre-notarized papertackles the problem of originality, by ensuring the originality of themedium, i.e., a sheet of paper, given its unique edge code identifier.

Referring to FIG. 13, document 200 includes edge code 202, text 204 andDataglyph 214 which holds a signed hash-value for the purpose ofauthentication and originality verification. Document 200 was createdusing pre-notarized paper, i.e., text 204 was printed or recorded on asheet of pre-notarized paper. In this example, pre-notarized paper wasproduced as follows during manufacture of the sheet of paper. The uniquesheet identifier 202 was applied to the paper's edge. Some measure ofsome chosen physical property(ies) of the sheet of paper was taken. Thistaken measure was stored in a measure database and indexed by the sheetunique identifier 202.

In FIG. 13, the process for authenticating the document 200, i.e.,whether the text is authentic, is shown. The edge code 202 is read in anedge reader and used with a portion of text 204 to create a new hashvalue 216. Dataglyph 214 is read and decrypted using public key 220 indecryption engine 222 to generate the original hash value. The originalhash value is compared in comparator 224 with the new hash value 216. Ifthe result 226 of the comparison indicates the two are substantiallyequal (within the level of loss tolerated by the encryption algorithm),the content (text) of the document 200 is authentic.

The next step is to verify that the document is original, i.e., that thesheet of paper is the same one used when the document 200 was created.Referring to FIG. 14, the edge code 202 is read by an edge reader. Theedge code 202 is provided to a database access 230 which consultsmeasure database 232. Measure database retrieves the physical propertiesmeasured 234 for that sheet of material indexed by the edge code 202.Given the type of physical properties measured at production time, thosesame measurements are made again to produce physical measures 236.Measures 234 and 236 are compared in comparator 238. If the result 240is substantially equal, the paper is original.

This solution to the joint-problem of authentication and originality ofhardcopy or physical documents incorporates the unique edge codeidentifier of the sheet in the authentication, content-based,hash-value. The verification consists of reading the edge identifier,computing again the hash-value given the identifier and the documentcontent, and finally validating the computed hash-value against theprinted hash-value using the cryptographic public key. This methodprevents manipulation of the content and prevents copy of the documentbecause the sheet identifier cannot be forged.

The strength of this method relies on the difficulty of producing asheet of paper having both a given identifier and some given physicalproperties. With respect to the physical measure, the edge itself may beused as the physical property or characteristic that discriminates eachindividual sheet. For example, the edge mark (identifier) applied on theedge involves applying some type of ink or dye on the edge. The way theink or dye penetrates the paper edge is presumably difficult to forgeand can therefore be a valuable measure. Alternatively, the state of the“surface” of the edge and its geometry constitutes a unique profile. Anadvantage to using the physical characteristics of the edge comes fromthe imposed usage of an edge reader (to read the edge unique identifier)at various steps of the method. If some of these edge readers are alsoable to adequately measure the characteristics above, they will servetwo purposes in one operation, both for the paper producer and for theconsumer.

There are many schemes for managing the measure database. The databasemay be managed by the paper producer that provides a service allowingthe consumers to check the validity of the sheet identifiers. Thedatabase may be managed by a notarial service run by a third party. Theconsumer may purchase the pre-notarized paper together with the recordof the physical measures. However, in this case, the notarization mayprobably be valid only internally to the customer organization.

The initial physical measures can be entirely recorded, for example, asa compressed very high-resolution picture of the pre-marked edge. Thecomparison of the physical measures is then possibly made on the entiremeasure, i.e., on the entire edge and not just a portion. The level ofcomparison may be user defined. For example, the consumer may makemeasures that are less accurate than the ones taken at production timewhile still being able to compare the two. This has a positiveimplication in term of cost for the consumer (cheaper machinery, fasterto operate). The invention separates the originality of the medium fromthe authentication of the content.

The digital signature can include the unique identifier andcontent-based information, regardless of the size and type of physicalmeasures. This leads to either a smaller footprint of the digitalsignature or an increased accuracy for the content representation (e.g.a bigger hash-value of the text). Quick and cheap verifications of theoriginality can be made by reading the sheet unique identifier andchecking it together with the document content against the signedhash-value (without taking any physical measure). The strength of theoriginality verification is directly dependent on the difficulty for aforger to mark a given identifier on the edge of a sheet of paper.However, if special ink may be used, it may require an uncommoninfrastructure and know-how. Similarly, a consumer might avoid verifyingthe originality of the sheet (avoid taking any physical measure) whencomputing the hash-value for a document, to make it easier and cheaper.The paper producer may keep secret some of the measures taken as anadditional protection against forgery of the paper. But some of theproperties should be public, to allow the consumers to run their ownverification with their own devices if they want to do so. The choice ofthe physical properties to measure can evolve over time almosttransparently for consumers, while increasing quality of paperpre-notarization.

The invention has been described with reference to particularembodiments for convenience only. Modifications and alterations willoccur to others upon reading and understanding this specification takentogether with the drawings. The embodiments are but examples, andvarious alternatives, modifications, variations or improvements may bemade by those skilled in the art from this teaching which are intendedto be encompassed by the following claims.

What is claimed is:
 1. An encoded sheet material, comprising: a sheet ofmaterial having a first surface, a second surface disposed opposite thefirst surface and an edge extending between the first surface and thesecond surface and peripherally about the sheet of material, the edgehaving unique indicia arranged thereon to form a unique code uniquelyidentifying the sheet of material, wherein the indicia are pre-markedduring fabrication of the sheet material.
 2. The encoded sheet materialof claim 1, wherein the code is 64 bits long.
 3. The encoded sheetmaterial of claim 1, wherein the code is visible.
 4. The encoded sheetmaterial of claim 1, wherein the code is invisible.
 5. An encoded sheetmaterial, comprising: a sheet of material having a first surface, asecond surface disposed opposite the first surface and an edge extendingbetween the first surface and the second surface and peripherally aboutthe sheet of material, the edge having unique indicia arranged thereonto form a unique code uniquely identifying the sheet of material,wherein the indicia are marked on the edge after information is recordedon one of the first and second surfaces.
 6. An encoded sheet material,comprising: a sheet of material having a first surface, a second surfacedisposed opposite the first surface and an edge extending between thefirst surface and the second surface and peripherally about the sheet ofmaterial, the edge having unique indicia arranged thereon to form aunique code uniquely identifying the sheet of material, wherein theindicia are readable by a scanner device operably connected to, and inconjunction with, a computer-implemented processor,and whereininformation is recorded on one of the first and second surfaces.